The Fay-Prince trap augmented with carbon dioxide (F-P/CO2) collected high numbers of male and female Aedes sierrensis (Ludlow). The F-P/CO2 trap collected 15-20 times more males, but statistically similar numbers of females as did a rabbit-baited CO2 trap (R/CO2). Carbon dioxide was essential to the successful operation of the F-P/CO2 trap for the collection of male and female Ae. sierrensis. A repeated measures ANOVA with polynomial contrasts found no significant differences in the population trends of female Ae. sierrensis measured by the two traps. Trap location also was a major source of variability, with one of the four locations accounting for 50% of all Ae. sierrensis collected. These results indicated that the F-P/CO2 trap was a simple but effective method for sampling Ae. sierrensis.